A21-12 Blind Bolt / Blind Nut Anvil, Standard Length. This standard length anvil is manufactured with hardened tool steel. This anvil is a component of the Blind Nut ”J” Type Standard Driving Tool assembly for use with a Hi-Shear® BG2500 hydraulic power gun. Anvil heads are designed to seat against the shapes and diameter sizes of the sleeve heads of blind nuts and blind bolts.